Originally Posted by jamesxEDGE
in california? I just got a notice that I need to get my smog check and I'm not running a muffler. Do i need one to pass?
Google is your friend.
Can I legally replace an emissions sensitive part on my car with an aftermarket product?
In the state of California, it is not legal to replace an emissions sensitive device without the replacement part having an exemption from CARB. Although replacing a particular device might have no apparent effect on the emissions, and the car might even pass a tail pipe "smog-check", the replacement part is still not considered emissions legal. In many cases, the mandatory visual inspection of the vehicle prior to an official state required smog-check may result in immediate failure of the test if a non-exempt part is identified.
A part that has been issued a CARB exemption has been subjected to strict laboratory testing as required by CARB in order to demonstrate that the replacement part will not increase emissions. (These tests are NOT the same as the "smog check" test and often require "cold start" testing procedures in order to test the efficiency of the emissions system during the initial seconds of the start-up cycle.) A part that has successfully passed these tests will be appointed an Executive Order number and will be listed on the CARB website for reference. Every Executive Order part or modification has an assigned number that can be verified by Smog Check stations, BAR Referee stations, or by the ARB. This number should be displayed on or near the emissions sensitive part for reference by a smog check technician.
For a database listing of current exempt parts, visit:
There are 3 components to the test:
None of the tests can begin until they locate and scan your BAR sticker. If you lack this sticker it means you have an out of state vehicle that has never been tested or it has been removed. You must make an appointment with the smog referee in this situation.
The air-gasoline combustion chemical equation is surprisingly complicated but general air quality is effected by three emissions: hydrocarbons (HC), carbon monoxide (CO) and various nitrous oxides (NOx). The sniffer has the ability to detect all three emissions simultaneously.
The emissions test is where they insert a probe into the tailpipe to sniff for combustion byproducts and attach a coupler to any spark plug wire to measure engine rpm. With those two items attached they begin the test on the dyno.
The computer automates the testing and the smog tech simply uses a remote control to communicate with the computer from the driver's seat. The first stage revs the engine to 15 mph and they hold it there while the sniffer does its job. The tech has to shift the bus into 2nd gear to accomplish this. The computer then cues the tech to bring the engine to rest for the second run. The second time, the steps are repeated until the computer requests the speed be raised to 25mph for a few moments (3rd gear).
Each smog testing shop is supposed to calibrate their tester every 72 hours. Be sure to ask them about it. I don't know if the computer compensates for temperature variations but that would be something you could ask as well. They are also supposed to use a large cooling fan above 72F ambient temperature but since we don't have a radiator this isn't necessary.
After the dyno testing, they perform a visual inspection. The visual inspection determines if any emission devices that were factory installed are missing. Although the list is long, only a subset applies to each model but if you are missing any item you will fail the test, unless the smog technician fails to notice that you require it when it's missing (don't gamble that this will happen for you). How can this happen? Because these vehicles were built before a lot of smog technicians were even born, many find the engine compartment unfamiliar.
The functional inspection includes a check of the timing and idle speed. The idle speed has to be within the manufacturer's guidelines and the timing has to be within 3 degrees of the specification otherwise you will fail. This is the simplest of tune-ups to perform but surprisingly, people drive to the testing center, cross their fingers and fail anyway. They also test the gas cap to see if it seals and check for the presence of any fuel pipe restrictors if applicable.
Be sure they know how to test the timing by clamping onto spark plug wire #1 or #3. If the do not, the timing mark will not appear and they may simply decide to fail you when the timing is indeed within spec.
A few years ago, the visual inspection was done first. At that time the testing was aborted any time you failed one of the stages in order. The benefit to the owner was that if you failed for something simple you wouldn't risk being tagged as a gross polluter (if you produced excessive emissions). The problem for the government was that they failed to collect any tailpipe emissions data in the process.
5. Visual Test:
The visual inspection is a check for the emissions items installed by the factory. It's sometimes followed by a functional test of that item.
This is a complete list of the codes taken from the Mitchell Applications Guide used by the smog testing system (CARB). They appear on your smog sticker.
Code Item Description
MFI Fuel Injection All Bosch L-Jetronic (VW AFC) components
PCV Positive Crankcase Ventilation Routes crankcase fumes to intake (to burn)
ACL Thermostatic Air Cleaner Intake air is heated by exhaust (via intake pipe) during warmup to reduce emissions
EVAP Fuel Evaporative System Connects fuel tank to intake for vapor recovery (to burn)
SPK Spark Ignition Control All advance, retard hardware and hoses
EGR Exhaust Gas Recirculation System Connects exhaust to intake to reduce NOx
OC Oxidation Catalytic Converter Converts HC, CO and O2 to CO2 and H20
FR Fill Pipe Restrictor Prevents leaded fuel pump nozzle from being used to fill tank (ruins CAT)
O2S Oxygen sensor Exhaust mounted sensor that dynamically adjusts air fuel ratio
AP Air Pump Injection System Crank driven pump that injects air into exhaust port
AIS Air Injection system Similar to AP but without pump
TP Throttle Positioner Corrects for altitude variations
CEC Computerized Engine Controls Electronic ignition (no points, no condenser)
EVAP-VC EVAP Vapor Canister Charcoal canister in engine compartment
SPK-DDD Spark Dual Diaphragm Distributor DVDA distributor vs. SVDA or purely mechanical (009)
SPK-TCS Transmission Controlled Spark Vacuum advance cutoff transmission switch
[Nothing about a muffler in there..]
Adequate Muffler Required
27150. (a) Every motor vehicle subject to registration shall at all times be equipped with an adequate muffler in constant operation and properly maintained to prevent any excessive or unusual noise, and no muffler or exhaust system shall be equipped with a cutout, bypass, or similar device.
(b) Except as provided in Division 16.5 (commencing with Section 38000) with respect to off-highway motor vehicles subject to identification, every passenger vehicle operated off the highways shall at all times be equipped with an adequate muffler in constant operation and properly maintained so as to meet the requirements of Article 2.5 (commencing with Section 27200), and no muffler or exhaust system shall be equipped with a cutout, bypass, or similar device.
(c) The provisions of subdivision (b) shall not be applicable to passenger vehicles being operated off the highways in an organized racing or competitive event conducted under the auspices of a recognized sanctioning body or by permit issued by the local governmental authority having jurisdiction.
Amended Ch. 558, Stats. 1977. Effective January 1, 1978. Supersedes Ch. 579.
Smog check might NOT require it, but registering your truck sure does.
Check this out as well!
CA. V.C. 27151 No person shall modify the exhaust system of a motor vehicle in a manner which will amplify or increase the noise emitted by the motor of such vehicle so that the vehicle is not in compliance with the provisions of Section 27150 or exceeds the noise limits established for the type of vehicle in Article 2.5(commencing with Section 27200) of this chapter. No person shall operate a motor vehicle with an exhaust system so modified.
CA. V.C. 27150 (a) Every motor vehicle subject to registration shall be equipped with an adequate muffler in constant operation and properly maintained to prevent any excessive or unusual noise, and no muffler or exhaust system shall be equipped with a cutout, bypass, or similar device.
You need to put a muffler on your setup as presently you have a ' bypass ' setup ( a pipe without a muffler ).
You need to know the laws in your state mate. Your state has a NICE website with good info! You should go browse it.